1. Field of the Invention
The present invention generally relates structures and methods for fabricating semiconductor devices, and more particularly to a structure and a method for mounting a flip-chip semiconductor device in which an under-filler is introduced into a space between a semiconductor chip and an wiring layer and a space between the wiring layer and a mounting substrate such as a printed circuit board.
In recent years, with increasing demand for miniaturization, lightweight and thinness of electronic apparatuses, semiconductor devices, which are used therein, have been produced smaller, lighter and thinner. For this reason, semiconductor devices, which are package types such as BGA (Ball Grid Array), CSP (Chip Size Package), MCM (Multi Chip Module) and the like, have been developed.
With regard to internal connecting we processes thereof, a wire bonding process and a flip-chip mounting process are generally employed.
It is predicted, however, that the flip-chip mounting process is becoming the mainstream in terms of its supporting area-pads and multi-bins and of being available to shorten lengths of wires.
It should be noted that, by the flip-chip mounting process, a plurality of protruding electrodes are formed on a surface of a semiconductor chip on which various semiconductor elements are formed and the electrodes are connected to an interconnecting substrate in a face-down state. In such a face-down state, however, since the protruding electrodes directly receive a stress resulting from a difference in thermal expansion coefficients between the semiconductor chip and the interconnecting substrate, there brings about a problem that the protruding electrodes cannot stand such a stress, for example, in a temperature cycling test or the like.
In general, after the flip-chip mounting process is completed, an under-filler is introduced into a space between the semiconductor chip and the interconnecting substrate so as to increase a contact area therebetween and relax the stress applied to the protruding electrodes. Mostly, with respect to flip-chip type semiconductor devices such as BGA, CSP and MCM, during a secondary mounting for mounting them on the printed circuit board, the further under-filler is introduced into the space therebetween so that connecting reliability can be ensured after the secondary mounting.
2. Description of the Related Art
FIG. 1A shows a conventional semiconductor device 10A. FIG 1B shows a state in which the semiconductor device 1OA is mounted on a motherboard 19 serving as the printed circuit board.
As shown in FIG. 1A, the semiconductor device 10A is a BGA-and-CSP package type semiconductor device, and generally comprises a semiconductor chip 11, a flexible printed substrate 12, a plurality of solder balls 13, and a first under-filler layer 18.
The semiconductor chip 11 has a circuit-forming surface (a bottom surface thereof in diagrams) on which a plurality of bumps 14 are provided. The bumps 14 are respectively soldered to a plurality of bonding pads 16 of the flexible printed substrate 12, which serves as an wiring substrate. Thus, the semiconductor chip 11 is mounted on the flexible printed substrate 12 in a face-down state by a flip-chip mounting process (a primary mounting).
Further, on the flexible printed substrate 12 are formed a plurality of connecting holes 17, positions of which are determined by respective connecting positions of the solder balls 13 to be described later. Moreover, on the flexible printed substrate 12 are formed wiring patterns 15, each having one end integrally connected to the bonding pad 16 and the other end connected to a connector plug filling the connecting hole 17.
The solder balls 13 serve as connecting terminals and are soldered to a surface opposite to a chip-carrying surface of the flexible printed substrate 12. The solder balls 13 are connected to the wiring patterns 15 through the connecting holes 17, respectively. Accordingly, the semiconductor chip 11 and the solder balls 13 are electrically connected over the flexible printed substrate 12, which serves as the interconnecting substrate.
Also, the first under-filler layer 18 is formed by introducing the under-filler, which is formed of resin, into a space between the semiconductor chip 11 and the flexible printed substrate 12. Thus, by forming the first under-filler resin layer 18 in the space therebetween, the bumps 14 can be reinforced. Accordingly, the bumps 14 can be prevented from being detached from the flexible substrate 12, even though a stress resulting from the difference in thermal expansion coefficient therebetween is applied thereto.
The previously described semiconductor device 10A, as shown in FIG. 1B, is mounted on the motherboard 19 by soldering the solder balls 13 to respective connecting electrodes 21 thereof. This is regarded as a secondary mounting. During the secondary mounting, the under-filler is introduced into a space between the flexible printed substrate 12 and the motherboard 19 so as to form a second under-filler resin layer 20 therewithin. Thus, connection reliability of the solder balls 13 can be improved.
A semiconductor device 10B shown in FIG. 2A, similar to the semiconductor device 10A shown in FIG. 1A, is a face-down semiconductor device belonging to the conventional BGA and CSP types. However, the semiconductor device 10B is provided with a printed wiring substrate 23 instead, serving as the interconnecting substrate.
The semiconductor chip 11 is, in a face-down state, connected to the printed wiring substrate 23, upon which a plurality of the bonding pads 16 are formed, whereas under which a plurality of boll pads 22 are formed. The bonding pads 16 and the ball pads 22 are connected through not-shown through-holes.
The bonding pads 16 are connected to the semiconductor chip 11 via the respective bumps 14. In order to relax the stress applied to these bumps 14, the under-filler resin is introduced into a space between the semiconductor chip 11 and the printed wiring substrate 23 so as to form the first under-filler layer 18. Further, the solder balls 13 are respectively soldered to the ball pads 22 which are formed on the lower surface of the printed wiring substrate 23. Thus, the semiconductor chip 11 and the solder balls 13 are electrically connected by the printed wiring substrate 23 serving as the interconnecting substrate.
By soldering the solder balls 13 to the respective connecting electrodes 21 of the motherboard 19, the previously described semiconductor device 10B, as shown in FIG. 2B, is mounted thereon. This is regarded as the secondary mounting. During the secondary mounting, the under-filler resin is introduced into a space between the printed wiring substrate 23 and motherboard 19 so as to form the second under-filler resin layer 20 therewithin. Thereby, the connection reliability of the solder balls 13 can be improved.
FIGS. 3 through 6 are diagrams showing a conventional method for producing a semiconductor device and a conventional method for mounting the same. The semiconductor device 10B, which have been described with reference to FIG. 2, is now used as an example in the following description of the conventional methods.
FIG. 3A is a flowchart showing the method for producing the semiconductor device 10B. The producing method proceeds as follows.
Firstly, at Step 10 (xe2x80x9cStepxe2x80x9d simply referred as to xe2x80x9cSxe2x80x9d in the diagrams), a well-known producing process is performed on a wafer so as to produce a plurality of the semiconductor chips 11 thereon. And then, at Step 11, a bump-forming process is performed so as to form a plurality of the bumps 14 on the semiconductor chips 11 which have been produced at Step 10. Thereafter, at Step 12, a dicing process is performed to dice the wafer so as to individualize the semiconductor chips 11 thereon.
In addition, at Step 13, a separate process is in advance performed so as to form the printed wiring substrate 23 serving as the interconnecting substrate. Then, at Step 14, a flip-chip mounting process is performed so as to mount the semiconductor chip 11 on the printed wiring substrate 23. Thereafter, at Step 15, an under-filler introducing process is performed for introducing the under-filler resin into the space between the semiconductor chip 11 and the printed wiring substrate 23 so as to form the first under-filler resin layer 18 therewithin.
After the introducing process is completed, at Step 16, a soldering process is performed so as to solder a plurality of the solder balls 13 under the printed wiring substrate 23. Then, at Step 17, a cleaning process is performed so as to remove solder pastes used at Step 16. Thereafter, the semiconductor device 10B is produced at Step 18. Thus, the conventional method for producing the semiconductor device 10B is completed.
FIG. 3B is a flowchart showing the conventional method for mounting the semiconductor device 10B, which is produced as described previously, on the motherboard 19 serving as the printed circuit board. The mounting method proceeds as follows.
At Step 20, a separate process is in advance performed so as to produce the motherboard 19.
At Step 21, a solder-paste is printed so that the solder paste is provided on the connecting electrodes 21 formed on the motherboard 19. Then, as Step 22, a carrying process is perform as shown in FIG. 4 so as to carry the semiconductor device 10B on the motherboard 19 by carrying the solder balls 13 on the respective connecting electrodes 21 with the solder pastes serving as adhesives printed thereon. This carrying process is regarded as a temporary mounting process.
At Step 23, a soldering process is performed such that the semiconductor device 10B, which is thus carried on the motherboard 19, is put into a reflow furnace so as to solder the solder balls 13 to the respective connecting electrodes 21. By Step 23, the semiconductor device 10B is firmly carried on the motherboard 19 as shown in FIG. 5. Thereafter, at Step 24, the cleaning process is performed so as to remove the solder pastes.
As shown in FIG. 5, after Steps 23 and 24 are completed, a space 24 is formed between the printed wiring substrate 23 and motherboard 19. Therefore, at Step 25, an under-filler introducing process is performed for introducing the under-filler resin into the space 24 therebetween so as to form the second under-filler resin layer 20.
FIG. 6 shows a state where the under-filler used to form the second under-filler resin layer 20 is being introduced into the space 24 therebetween. And when the second under-filler layer 20 is completely formed within the space 24, the method for mounting the semiconductor device 10B on the motherboard 19 is finished.
In addition, with respect to the semiconductor device 10A shown in FIG. 1, it can be produced and mounted by the same methods as described with reference to FIGS. 3 through 6, only except the printed wiring substrate 23 is replaced with the flexible printed substrate 12.
However, according to the conventional producing and mounting methods, the under-filler introducing process is performed two times, one time at Step 15 of the producing method where the under-filler is introduced to form the first under-filler resin layer 18, the other time at Step 25 of the mounting method where the under-filler is introduced to form the second under-filler resin layer 20.
In other words, conventionally, the first under-filler layer 18 and the second under-filler layer 20 are formed separately by the two separate processes. For this reason, the producing and mounting of the semiconductor device 10B becomes complicated on the whole and thereby brings about a problem of an increase in the costs thereof.
Further, according to the conventional method, after the first under-filler resin layer 18 is formed at Step 15, the soldering process is performed at Step 16 and Step 23. Further, with respect to the flip-chip type BGA, CSP and MCM semiconductor devices, the semiconductor chip 11 thereof is connected in the facedown state and the under-filler used to form the first under-filler resin layer 18 is introduced into the space between the semiconductor chip 11 and the interconnecting substrate (the flexible printed substrate 12 or the printed wiring substrate 23).
For the above-mentioned reasons, in a case where the interconnecting substrate is formed of a water-tight material, during the above-mentioned soldering process, water contained in the first under-filler resin layer 18 is heated and changed into water vapor. Since the water vapor has not a path to flee efficiently, there may bring about a problem that a popcorn phenomenon (an air-bladder phenomenon) occurs. When the popcorn phenomenon occurs, at the worst, cracks may occur between the semiconductor chip 11 or the interconnecting substrate and the first under-filler layer 18, and as a result, mounting reliability is deteriorated.
It is a general object of the present invention to provide a mounting structure and a mounting method of a semiconductor device, in which the above problems are eliminated.
Another and more specific object of the present invention is to provide a mounting structure and a mounting method of a semiconductor device, which can realize simplification of the producing and mounting thereof.
Still another object of the present invention is achieved by a semiconductor device comprising: a semiconductor chip having a device surface; an interconnecting substrate carrying said semiconductor chip in a face-down state, such that said device surface faces a top surface of said interconnection substrate with a gap formed between said device surface and said top surface; a plurality of connecting terminals provided on a bottom surface of said interconnecting substrate; and at least one through-aperture formed in said interconnecting substrate so as to penetrate from said bottom surface to said top surface, said through-aperture being formed in an area of said interconnecting substrate and covered by said semiconductor chip.
Still another object of the present invention is achieved by a structure for mounting a semiconductor device, the semiconductor device comprising a semiconductor chip having a device surface; an interconnecting substrate carrying said semiconductor chip in a face-down state, such that said device surface faces a top surface of said interconnection substrate with a gap formed between said device surface and said top surface; a plurality of connecting terminals provided on a bottom surface of said interconnecting substrate; at least one through-aperture formed in said interconnecting substrate so as to penetrate from said bottom surface to said top surface, said through-aperture being formed in an area of said interconnecting substrate and covered by said semiconductor chip; a main substrate to which said connecting terminals face; and a first under-filler layer formed between said semiconductor chip and said interconnecting substrate and a second under-filler layer formed between said interconnecting substrate and said main substrate, communicating with each other via said through-aperture.
Still another object of the present invention is achieved by a method for mounting a semiconductor device on a mounting substrate, the semiconductor device comprising a semiconductor chip having a device surface; an interconnecting substrate carrying said semiconductor chip in a face-down state, such that said device surface faces a top surface of said interconnection substrate with a gap formed between said device surface and said top surface; a plurality of connecting terminals provided on a bottom surface of said interconnecting substrate; and a main substrate to which said connecting terminals face; the mounting method comprising the step of:
forming at least one through-aperture in said interconnecting substrate so as to penetrate from said bottom surface to said top surface, said through-aperture being formed in an area of said interconnecting substrate and covered by said semiconductor chip;
connecting said connecting terminals of said semiconductor device to said main substrate; and
introducing an under-filler from one of a space between said semiconductor chip and said interconnecting substrate and a space between said interconnecting substrate and said main substrate, and thereby introducing said under-filler layer into the other space via said through-aperture.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.